Target and circuit for storage tubes



NOV. 18, 1952 u R. sNYDER, JR

TARGET AND CIRCUT FOR STORAGE TUBES Filed April 12, 1945 INVENTOR..fafa/ez; J1:

ATTORNEY. v

Patented New. 18, 1952 2.618.762 TARGET AND cinema* Foa STORAGE 'runasmener-e r.. snyder, Jr., Princwn, N. s., assignmto Radio Corporation ofAmerica, a corporation of Delaware Application April 12, 1945, SerialNo. 588,046

3 Claims. (Cl. 315-12) In storage tubes of the cathode beam type,

charges proportional to received signals have been built up on -elementsof a target by the action of an electron beam sweeping over them in onescansion and wiped off or neutralized in another scansion of the samebeam. When this neutralization takes place, a signalis produced' andimpressed on an indicating device. This prior art storage tube hasseveral disadvantages, chief among which is the introduction oftransientslinto the amplifying system by the sudden change of velocityof the beam.

. It is an object of my invention to construct a storage tube having onecathode beam gun for putting the signal on a target and an additionalcathode beam gun for taking it on.

Another object of the invention is to scan the put-on beam of a storagetube at a higher rate over the target than that of the take-off beam.

Another object is to scan the put-on beam over -the target to reduce thepositive reference potential thereof with suppressed secondary emissionin accordance with the received signal and to scan the take-off beamthereover to raise the potential to said reference potential by means ofsecondary emission.

Another object is to construct the storage tube target of a plurality ofinsulated conductors with arrangements for scanning both beamstransversely across the conductors independently of each other.

Another object is to construct the storage tube target of a plurality ofinsulated conductors with arrangements for scanning the put-on beam'transversely across one region of the conductors and the take-01T beamtransversely across another portion of the same conductors and at adifferent rate.

Other objects will appear in the following description, reference beinghad to the drawings, in which:

Figure l is a diagrammatic illustration of the tube.

Figure 2 is an elevation of a portion of the target and shield grids.

Figure 3 is a section taken on the line 3-3 vof Figure 2, viewed in thedirection of the arrows.

In Figure 1, the evacuated envelope and supporting structure of theelements in the tube are omitted, as these are well known and may be ofany suitable material and design. The top gun I in this gure may havethe usual cathode 2 and ly enlarged for illustrative purposes.

.2 controlling the beam E. This control member, as usual, consists of acylinder of metal having a minute orifice in its end. This opening isgreat- The first anode 6 may be of standard metallic tubular construction, having a small orifice in the end adjacent the gun and aninternal wall having a suitable opening for constricting the beam thedesired amount. Adjacent the remote end of the rst anode is positionedthe second tubular anode l of somewhat larger diameter. Spacedhorizontal defiector plates 8, 9 are positioned in a wellknown way forhorizontally scanning the beam across the target, the front plate beingpartially broken away to show the back one. A variable voltage, ofsaw-tooth form, is impressed between these plates to produce thehorizontal motion of the beam, as well understood. Spaced verticaldeector plates I0, Il are used to position the beam on the desiredhorizontal line L. For this purpose the vertical deiiectors would have aconstant direct current voltage. Parallel shield plates I2, I3 arepositioned in front of the upper part of the target.

The target consists of a sheet of insulation It. such as a thin sheet ofmica, on which has been deposited parallel strips I5 of metal, forexample silver, deposited by photographic process or by any othermethod. The strips are relatively narrow and are preferably spaced aparta distance equal to three times their Width. Metal shield grids I6, I1are positioned at the top and bottom of the target and have prongs I8,I9 extending between the strips I5 and are preferably of the same widthas the strips, so that they may be spaced therefrom a distance equal totheir own width. A signal plate 20 is positioned on the side of the micaplate remote from the gun and is connected to any desired indicatingdevice 20', for example, the facsimile recorder disclosed in the patentof Charles J. Young, 1,848,862, March 8, 1932, though a visual indicatorsuch as an oscilloscope may also be used.

In the lower gun 2| the lower anodes, the deflector plates and shieldsmay have the same construction as in gun I and these parts have beengiven the same reference characters as similar heater 3. Aroundthecathodeis the grid 4 for ones in upper gun l, except that the subscripta has been added thereto to distinguish the ones from the others. Itwill therefore be unnecessary to specifically refer to the parts. Thisgun scans the beam 5a over the bottom of the target at the line L'extending across the strips I5. The two guns I and 2| enclosed in theevacuated envelope (not shown) are electrostatically separated by acentral shield plate 22.

The cathodes of both guns may have a negative potential of 1,000 volts,the first anodes about -800 volts and the second anodes have thepositive groundpotential. The shields I2, I3 and I 8 may bevoltsn'egative and the shields I2a,

known manner.

Ila and IJ 100 volts positive.

Thesey are mentioned merely as examples.

One of the guns, say the top gun I, will have a.

quency of an associated radar equipment, say 400 cycles per second. Theother gun will have its similar plates energized by a saw-tooth voltageof some lower frequency, Isuch as 2 cycles per second, which coincideswith the scanning frequency of the recording device 20'.. A y Theoperation may be described as follows: A signal pulse, sent out at thestartof each cycle of the saw-tooth generator 23 by a keyer andtransmitter T, is reflected by aircraft, ships and other objects back tothe receiver 24, in which the echoes are amplified and detected in'These devices may be of any known type and are illustrated in blockdiagram. I'l` antennae are preferably of the directional type. such asdipoles indicated. The detected and amplified signals modulate the beamof gun I as it sweeps across the strips I5 along line L. The electronsof beam 5 landing on the floating elements I5, which have beenpreviously charged to a positive reference potential, as laterdescribed, diminish the positive charge. The diminishing of this charge(or the driving of the elements negative) occurs when the beam strikesthese elements because the shields I2, I3 and I8 are negative relativeto the floating elements and. therefore, suppress the emission ofsecondary electrons released by the impact of the beam. 'I'he repeatedscanning of the mosaic by this puton beam increases the charge due tosignals on each successive cycle. The charges induced by noise in thesignal which does not occur at the same point in successive cycles issmoothed out.

` While the storing of the signals by beam 5 goes on withoutinterruption, the take-oil' and reproducing beam 5a of the lower gunrecharges at each sweep the floating elements to a positive referencepotential determined by the shields IZa, Ila and II. The recharging isaccomplished by means of secondary emission from the floating elements.When the beam 5a strikes the elements, it releases a preponderance ofsecondary electrons. These electrons are attracted by the positivefields of the shields until the potential lof the-elements rises to thatof the shields. When Vthis occurs, acollecting field no longer existsaround the elements and the secondary emissionratio falls to unity. Thereproducing beam v5a is sufficiently intense to over-ridge in one sweepany signals which may have been recorded by the beam 5 of the upperrecording gun in its multiplicity of sweeps.

When the take-off beam 5a recharges the strips I5 to referencepotential, as just described, signals are impressed on recorder 20'. Ifthe echoes or signals are from a moving object, such as an airplane, forexample, they will be recorded as a diagonal line across the page of thefacsimile recorder, but those from stationary objects will haveunchanging phase and will be recorded in .vertical lines on the page. s

It will thus be seen that, in my improvement, the strength of desiredsignals is built up by storage before being recorded, but noise signalsare not, since they occur at random.

The storing and discharging of the signals may be opposite to thatdescribed, but the results are not so satisfactory. When the put-onbeamis thus-used to scan the elements of the target in the region of apositive collecting ileld to impress a positive charge thereon by virtueof emission of secondary electrons and the take-off beam scans them in anegative field to charge the elements. to a negative potential, then thestored signal will vary with variations in secondary emission ratio fromelement to element in the storing process. In the preferred method, anyvariation in emission ratio is. however, not objectionable in thetake-ofi' action, as the secondary emission ratio of theA elements isnecessarily made greater than unity and the take-off beam is made strongenough to over-ride any charge impressed by the put-on beam.

Various other modifications may be made without departing from thespirit of the invention. i Having described my invention, what IVclaim 1. In cathode beam storage tubes, a target consisting of a sheetof insulation, a multiplicity of' 'electrically isolated conductors ofrelatively high secondary electron emissivity extending across saidsheet and a shield grid at each'end having prongs extending b'etween theconductors and spaced therefrom.

2. In cathode beam storage tubes, a target consisting of a sheet ofinsulation, a multiplicity of electrically isolated conductors ofrelatively high secondary electron emissivity extending across saidsheet, a shield grid at each end having prongs extending between theconductors and spaced therefrom, means for applying a higher voltage toone grid than to the other, means for scanning a beam at a predeterminedrate across said conductors adjacent one grid and means forscanning'another beam across said conductors adjacent the other grid ata rate relatively lower than the first-mentioned rate.

3. In cathode beam storage tubes, a target consisting of a sheet ofinsulation, a multiplicity of electrically isolated conductors ofrelatively high secondary electron emissivity extending across saidsheet, a shield grid at each end having prongs extending between theconductors and spaced therefrom, means for applying a higher voltage toone grid than the other, means for scanning a beam at a predeterminedrate across said conductors adjacent one grid and means for scanning abeam across said conductors adjacent the Yother grid at a raterelatively lower than the RICHARD L. SNYDER, JR.

4 REFERENCES CITED l A The following references are of record in thefile of this patent:

-UNII'ED STATES PATENTS Number Name Date 2,072,658 Von Bronk Mar. 2,1937 2,130,134 Iams Sept. 13,1938 2,147,760 Vance et al Feb. 21, 19392,179,205 Toulon Nov. 7, 1939 2,186,393 Ring et a1. Jan. 9, 19402,250,528 Gray July 29, 1941 2,264,540 .Lubszynski Dec. 2,- 19412,273,433 Bruce Feb. 17, 1942 2,291,476 Kernkamp July 28, 1942 2,301,743Nagy et a1. Nov. 10, 1942 2,324,534 Pierce July 20, 1943 2,355,212Farnsworth Aug. 8, 1944

